Supply & return temperature measurement

In order to check whether our house was suitable for a heat pump, I needed to know the preheating temperature and set it so that it did not exceed 40°C.

I already have an ESP with a 4-channel relay board in the boiler room and had experience with the Dallas temperature sensor. So I connected two Dalles temperature sensors to the ESP relay board and displayed the values in Home Assistant. Both Dalles sensors can be connected to one pin.

To get the difference I’ve created a sensor with subtracts both values.

      - name: "DiffVorRückHZ"
        state: >
          {{states.sensor.rucklauf_hk1_2.state | float(0) - states.sensor.vorlauf_hk1_2.state |float(0) }}

Here is the code extension for the ESP:

dallas:
  pin: GPIO0
  update_interval: 20s

# Individual sensors
sensor:
  - platform: dallas
    address: 0x573ce1e3803d5328
    name: "Vorlauf HK1"
    unit_of_measurement: "°C"
    icon: "mdi:thermometer-plus"
    device_class: "temperature"
    state_class: "measurement"
    accuracy_decimals: 2
  - platform: dallas
    address: 0x473ce10457ed9628
    name: "Rücklauf HK1"
    unit_of_measurement: "°C"
    icon: "mdi:thermometer-minus"
    device_class: "temperature"
    state_class: "measurement"
    accuracy_decimals: 2

And here is the code for the dashboard:

type: horizontal-stack
cards:
  - type: gauge
    entity: sensor.vorlauf_hk1_2
    name: Vorlauf Heizung
    needle: true
    severity:
      green: 25
      yellow: 0
      red: 44
  - type: gauge
    entity: sensor.rucklauf_hk1_2
    name: Rücklauf Heizung
    needle: true
    severity:
      green: 25
      yellow: 0
      red: 44